Why is my DVR space not accurate? I have 5 2 hr movies yet it says 75% full????

Why does it show 75% full?   I only have 5 2 hr movies yet it show that.  And the % was showing 80% a couple of days ago but this is just dumb.   I will check back in a week or 2 for an answer as I did a search for dvr and almost every reply was a link or a repeat of the posting with no replies from months ago.